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X-ORIGINAL-URL:https://web-f1.ijs.si
X-WR-CALDESC:Events for Department of Theoretical Physics
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TZID:Europe/Ljubljana
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DTSTART:20240331T010000
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DTSTART:20241027T010000
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BEGIN:VEVENT
DTSTART;TZID=Europe/Ljubljana:20240902T140000
DTEND;TZID=Europe/Ljubljana:20240902T150000
DTSTAMP:20260423T172819
CREATED:20240819T122059Z
LAST-MODIFIED:20240902T125507Z
UID:35397-1725285600-1725289200@web-f1.ijs.si
SUMMARY:Jan Rozman\, "From Substrate Dissipation to Internal Dissipation Vertex Model Dynamics: Generating Sustained Flows"
DESCRIPTION:Speakers: Jan Rozman\nComplex tissue flows in epithelia are driven by intra- and inter-cellular processes that generate\, maintain\, and coordinate mechanical forces. There has been growing evidence that cell shape anisotropy\, manifested as nematic order\, plays an important role in this process.  Here we extend an active nematic vertex model by replacing substrate friction with internal viscous dissipation\, dominant in epithelia not supported by a substrate or the extracellular matrix\, which are found in many early-stage embryos.  When coupled to cell shape anisotropy\, the internal viscous dissipation allows for long-range velocity correlations and thus enables the spontaneous emergence of flows with a large degree of spatiotemporal organisation. We demonstrate sustained flow in epithelial sheets confined to a channel\, providing a link between the cell-level vertex model of tissue dynamics and continuum active nematics\, whose behaviour in a channel is theoretically understood and experimentally realisable. Our findings also show a simple mechanism that could account for collective cell migration correlated over distances large compared to the cell size\, as observed during morphogenesis.\nhttps://indico.ijs.si/event/2245/
URL:https://web-f1.ijs.si/event/jan-rozman-tba/
LOCATION:C/2-X – F1 čajnica (Jamova)
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Ljubljana:20240903T140000
DTEND;TZID=Europe/Ljubljana:20240903T150000
DTSTAMP:20260423T172819
CREATED:20240819T122059Z
LAST-MODIFIED:20240903T125748Z
UID:35398-1725372000-1725375600@web-f1.ijs.si
SUMMARY:Somiealo Azote\, "Quantitative Predictions of biomechanical drivers of cell delamination in stratified epithelia (skin epidermis) using a dynamic 3D vertex model"
DESCRIPTION:Speakers: Somiealo Azote\nDuring embryonic development\, the skin epidermis gradually transitions from a single layer of stem cells to a stratified\, multi-layered tissue. This process involves the coordinated differentiation and upward movement of basal cells\, known as delamination. It is not clear what mechanisms control this differentiation and delamination\, allowing cells to move upward across the sharp basal-suprabasal boundary to regulate stratified tissue self-renewal and homeostasis. Although some delamination events are coupled to cell division\, we first focus on the simpler case where delamination occurs in the absence of cell division\, and develop a biomechanical model to investigate several experimentally driven hypotheses for what drives delamination in those cases: i) changes in the adhesion of basal cells to extra cellular matrix in the basement membrane\, ii) local fluidization of surrounding tissue due to fluctuations or nearby cell divisions\, or iii) cell autonomous changes to cell-cell adhesion and cortical tension. Experimental data from the developing mammalian epithelium in the Niessen and Wickström labs have identified specific changes to the transcriptome of cells committed to delamination. Many of these changes are associated with cell-cell and cell-substrate adhesion pathways. We incorporate them in the computational models as changes to the model parameters describing heterotypic and homotypic cell-cell interfacial tensions and adhesion to substrate. We make quantitative predictions for cell shape\, delamination probabilities\, and delamination rates that we compare directly to experiments\, in both control and perturbed systems\, to determine how different mechanisms are driving delamination.\nhttps://indico.ijs.si/event/2244/
URL:https://web-f1.ijs.si/event/somiealo-azote-quantitative-predictions-of-biomechanical-drivers-of-cell-delamination-in-stratified-epithelia-skin-epidermis-using-a-dynamic-3d-vertex-model/
LOCATION:C/2-X – F1 čajnica (Jamova)
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Ljubljana:20240905T140000
DTEND;TZID=Europe/Ljubljana:20240905T150000
DTSTAMP:20260423T172819
CREATED:20240623T113943Z
LAST-MODIFIED:20240905T122617Z
UID:30278-1725544800-1725548400@web-f1.ijs.si
SUMMARY:Shoji\, Baratella: The Standard Model lifetime is slightly shorter
DESCRIPTION:We revisit the decay rate of the electroweak vacuum in the Standard Model with the full one-loop prefactor. We focus on the gauge degrees of freedom and derive the degeneracy factors appearing in the functional determinant using group theoretical arguments. Our treatment shows that the transverse modes were previously overcounted\, so we revise the calculation of that part of the prefactor. The new result modifies the gauge fields’ contribution by 7% and slightly decreases the previously predicted lifetime of the electroweak vacuum\, which remains much longer than the age of the universe. Our discussion of the transverse mode degeneracy applies to any calculation of functional determinants involving gauge fields in four dimensions.\nhttps://indico.ijs.si/event/2176/
URL:https://web-f1.ijs.si/event/shoji-baratella-the-standard-model-lifetime-is-slightly-shorter/
LOCATION:https://zoom.us/j/3601731049?pwd=bVNQRjUxU2ExZ0cveWcxYXNUUGdjZz09 (F1 tea room)
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BEGIN:VEVENT
DTSTART;TZID=Europe/Ljubljana:20240912T140000
DTEND;TZID=Europe/Ljubljana:20240912T150000
DTSTAMP:20260423T172819
CREATED:20240827T122432Z
LAST-MODIFIED:20240912T130001Z
UID:36147-1726149600-1726153200@web-f1.ijs.si
SUMMARY:Pietro Baratella: Journal Club on WZW terms without anomalies: generalised symmetries in chiral Lagrangians
DESCRIPTION:Journal Club on WZW terms without anomalies: generalised symmetries in chiral Lagrangians (arXiv:2407.20340)Abstract:We consider a 4d non-linear sigma model on the coset $(text{SU}(N)_L times text{SU}(N)_R times text{SU}(2))/(text{SU}(N)_{L+R}times text{U})cong text{SU}(N) times S^2$\, that features a topological Wess–Zumino–Witten (WZW) term whose curvature is $frac{n}{24pi^2}text{Tr}(g^{-1}dg)^3 wedge mathrm{Vol}_{S^2}$ where $g$ is the $text{SU}(N)$ pion field. This WZW term\, unlike its familiar cousin in QCD\, does not match any chiral anomaly\,so its microscopic origin is not obviously QCD-like. We find that generalised symmetries provide a key to unlocking a UV completion.The $S^2$ winding number bestows the theory with a 1-form symmetry\, and the WZW term intertwines this with the $text{SU}(N)^2$ flavour symmetry into a 2-group global symmetry. Like a ‘t Hooft anomaly\, the 2-group symmetry should match between UV and IR\, precluding QCD-like completions that otherwise give the right pion manifold. We instead construct a weakly-coupled UV completion that matches the 2-group symmetry\, in which an abelian gauge field connects the QCD baryon number current to the winding number current of a $mathbb{C}P^1$ model\, and explicitly show how the mixed WZW term arises upon flowing to the IR. The coefficient is fixed to be the number of QCD colours and\, strikingly\, this matching must be `tree-level exact’ to satisfy a quantization condition.We discuss generalisations\, and elucidate the more intricate generalised symmetry structure that arises upon gauging an anomaly-free subgroup of $text{SU}(N)_{L+R}$. This WZW term may even play a phenomenological role as a portal to a dark sector\, that determines the relic abundance of dark matter.\nhttps://indico.ijs.si/event/2259/
URL:https://web-f1.ijs.si/event/pietro-baratella-journal-club-on-wzw-terms-without-anomalies-generalised-symmetries-in-chiral-lagrangians/
LOCATION:https://zoom.us/j/3601731049?pwd=bVNQRjUxU2ExZ0cveWcxYXNUUGdjZz09 (F1 tea room)
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Ljubljana:20240912T141500
DTEND;TZID=Europe/Ljubljana:20240912T151500
DTSTAMP:20260423T172819
CREATED:20240903T140241Z
LAST-MODIFIED:20240912T130001Z
UID:36702-1726150500-1726154100@web-f1.ijs.si
SUMMARY:Nataša Adžić\, "The role of effective interactions in predicting the exotic states of soft matter"
DESCRIPTION:Speakers: Nataša Adžič (Institute of Physics\, Belgrade)\n Studying static properties of colloidal suspensions is often a computationally expensive task due to their complex composition and interactions that appear at various length scales. Large macromolecules are surrounded by small solute particles and typically some other small components such as salt ions. One of the useful coarse-graining tools for studying self-organisation of macromolecules in solutions is the method of effective interactions. It is based on calculation of the effective Hamiltonian as a canonical trace over small degrees of freedom for the given fixed configuration of large ones . The calculated effective interaction can be further employed in Monte Carlo simulations between effective point particles that mimic behaviour of large macromolecules. In that way a fast scan of their phase organisation can be obtained. In this talk we will see how this method applies to self-organisation of various all-DNA dendrimers\, macromolecules composed solely of short segments of DNA chains .     R. Blaak\, B. Capone\, C. N. Likos\, and L. Rovigatti\, Accurate Coarse-Grained Potentials for Soft Matter Systems\, in Computational Trends in Solvation and Transport in Liquids – Lecture Notes\, IAS Series\, Vol. 28\, 2015. N. Adzic\, C. Jochum\, C. N. Likos\, and E. Stiakakis\, “Engineering Ultrasoft Interactions in Stiff All-DNA Dendrimers by Site-Specific Control of Scaffold Flexibility”\, Small 2023\, 2308763 (2024). E. Stiakakis\, N. Jung\, N. Adzic\, T. Balandin\, E. Kentzinger\, U. Rucker\, R. Biehl\, J. Dhont\, U. Jonas\, and C. N. Likos\, “Self Assembling Cluster Crystals from DNA Based Dendritic Nanostructres”\, Nat. Commun. 12\, 7167 (2021). N. Adzic\, C. Jochum\, E. Stiakakis\, G. Kahl\, C.N. Likos\, “Self-organisation of planar and tripod-shaped DNA stars confined to the water-air interface”\, in preparation for submission\nhttps://indico.ijs.si/event/2262/
URL:https://web-f1.ijs.si/event/natasa-adzic-the-role-of-effective-interactions-in-predicting-the-exotic-states-of-soft-matter/
LOCATION:Seminar room of physics (106) (IJS)
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Ljubljana:20240924T110000
DTEND;TZID=Europe/Ljubljana:20240924T120000
DTSTAMP:20260423T172819
CREATED:20240919T113033Z
LAST-MODIFIED:20240924T091052Z
UID:38210-1727175600-1727179200@web-f1.ijs.si
SUMMARY:Herbi Dreiner: Testing Locality via Bell's Inequality at Colliders?
DESCRIPTION:https://indico.ijs.si/event/2274/
URL:https://web-f1.ijs.si/event/herbi-dreiner-testing-locality-via-bells-inequality-at-colliders/
LOCATION:C/2-X – F1 čajnica (Jamova)
END:VEVENT
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